In existing ships including an internal combustion engine, thermal energy is generated as a result of combustion of fuel such as petroleum in the internal combustion engine, and then the thermal energy is converted into a propulsive force of ships. The combustion of fuel in the internal combustion engine generates an exhaust gas containing nitrogen oxide.
The exhaust gas generated in the internal combustion engine is discharged to the outside from the internal combustion engine through an exhaust line. The exhaust gas basically contains nitrogen oxide and therefore environmental factors need to be considered. In this regard, for example, Patent Document 1 discloses a technique of removing, by using a denitration device, nitrogen oxide from exhaust gas discharged to the outside from an internal combustion engine of ships.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2012-047096